Thermal overload relay



April Wm. H. L. VAN VALKENBURG 11352514 THERMAL OVERLOAD RELAY Filed Oct. 19, 1926 3 Sheets-Sheet l [/vvE/v TOR April 1930. H. L. VAN VALKENBURG 1,752,514

THERMAL OVERLOAD RELAY Filed Oct. 19, 1926 '3 Sheets-Sheet 2 Aprifi 1, EQBQ. H. L. VAN VALKENEURG 197529514 THERMAL OVERLOAD RELAY Filed Oct. 19, 1926 3 Sheets-Sheet 3 [/v I/E/V TOR flew/wow 1., M WILKE/VBUIFG Arm's.

tion is to tacle for Patented; Apr; 1, 1930 EERMON L. van vanxminuae, or

W'A'CI'TVA'JJOSA, WISCONSIN, ASSIGNOB, BY MESNE ASSIGNMENTS, TO SQUARE 1). COMPANY, 01? DETROIT, MICHIGAN, A GORPORA TION OF MICHIGAN Application filed October 19, 1926. Serial m..142,e25.

My invention relates to thermal overload relays and similar apparatus in which a detent. is normally heldin acting position by means of solder or other fusible material 5 which melts and releases the detent when heated beyond critical temperature, the fusible material being associated with an electric thermal element subject to electrical conditions in the line; One object of theinvenprovide an improved type of recepproved mounting'for the detent. Another ob ject is to provide a simple and effective form of heating unit bywhich the fusible mate- 15 rial, usually an alloy of low melting point,

I 20 heating the alloy receptacle and also forming the sole support for it. Another object is to causethe controlling or master switch to open with a quick break. Another object is to provide a simple and advantageous type of tripping mechanism by which all phases will be opened when the electrical energy inany vone of them becomes excessive. "Another object is to provide a tripping mechanism in which there are two. or more releasable detents and any one of them may release and trip the mechanism without disturbing the other detents and without being prevented'from operating by reason of the fact that none of t e others have released. As a result of this characteristic the detents may be said to be universally and independently operable. A furtherobject is to provide simple and effective means may be reset and normal operating conditions parent as the descri tion proceeds.

I accomplish my-o jects y the mechanism illustrated in the accompanying drawings, in which- 4 Figure 1 is a diagrammatic view showing the general arrangement of a system embodying theinvention.

Figure 2 is a perspective view of themelting pot and associated elements, together with the resetting bar and throwout switch.

the fusible material and an -im- I by which the tripping mechanism.

restored. .Further objects will become ap- THERMAL OVERLOAD RELAY Figure 3 is a section 5 Flgure 6 IS an elevation-illustratlng a modlfied orm of heating element, the view being substantially on the line 6-6 Figure 9.

Figure 7 is an enlarged sectional View on the line 77 Figure 6.

Figure 8 is a shown in Figures 6 to 9 inclusive.

Figure 9 is a plan section on the line 9-9 Figure 6. Figure 10 is a sectional elevation showing another modified type of heating element-for the melting pot.

Figure'll is a plan section on the line 11-11 Figure 10. Figure 12 is a p'ers ective view of-the type of heating element s own in Figure 11.

Figure 13 is an elevation of still another modified form of heating element for the melting pot. Figure 14 is a Figure-13.

Figure 15 is a perspective View of a type 14. The type shown in Figures 13 to 15 is similar to the type-shown in Figures 1 to 5 inclusive exceptthat the heatin element is much thicker and-therefore is a le to form 'a support for the melting pot as well as a heating element therefor.

plan section taken on the line perspective view showing the type of heating element employed in the form a. the line as Fig ure 2, showing the holding ratchet and asso plan section on line 14-14 conductors A, B, C lead to contacts 10, 11, 12 A respectively which are adapted to be engaged by the switch arms 13, 14, 15 respectively of the main switch. These are all controlled by a main switch-operating bar 18 which is normally urged by a spring 20 to open the main switch. From switch arm 13 a conductor 22 eads to the motor M. From switcharm 14 80 'of heating element shown in Figures 13 and a conductor 23 leads to the binding post 24 of a thermal unit presently to be described. From switch arm a conductor 25 leads to the terminal 26 of a secondthermal unit similar to the first.

The motor is connected by a conductor 27,,

to the terminal 28 of the first thermal unit and by the conductor 29 to the terminal 30 of the second thermal unit. The main switch is held closed under normal operating conditions by means of an electromagnet composed of a winding 32 having a movable core 33 fastened to a lever 34 which controls the switch. This winding is connected by a conductor 36 to the main conductor A. 'At the other end the winding is connected by a conmay be considered to be part of a holding circuit. 1 v

Contact 42 is connectedby a conductor 44 to a stop switch 46 adapted to engage a stationary contact 48 connected by a conductor 50 to a stationary contact 52 of a start switch 54. The latter is connected by a conductor 56 to a stationary contact 58 which in turn is connected by. a conductor 60 to the line conductor C. A switch arm 62 mounted on a pivot 64 connects contact 58 to a conductor 66 leading to the conductor 50. Switch arm 62 is pivotally connected to and operated by the main operating bar 18.

The master switch 40 is operated by a tripping bar 70 which has a notch 71 for engaging the end of the switch. This bar is lon itudinally slidable in stationary brackets 2. The tripping bar is free from bias longitudinally, that is, it tends to remain where positioned unless acted upon by some of the associated parts. In the diagram Figure 1 the bar is shown in normal operating position, that is, the position corresponding to closed position of the master switch 40. T will now describe the tripping mechanism and the construction of the thermo-electric units by which the tripping bar is operated to open the master switch and thus open the main switch when the current conditions in any one of the phases of the supply circuit become excessive.

Referring especially to Figures 2 to 5, there is in each of the units a ratchet wheel 80 rigidly secured-to a shaft 81 which is arranged vertically and at the lower end has a step bearing in the bottom of a receptacle or cup 82. This cup contains a metal alloy 83 especially selected so that it will soften suficiently to release shaft 81 when heated to a predetermined or critical temperature, corresponding to maximum permissible current conditions in the supply conductors A,

upper end of the latter. Thus the receptacle 4 has a roomy chamber for holding the alloy and affords both a vertical and lateral bearing for the shaft. This forms a simple and efiicient mounting for the ratchet wheel and shaft, and avoids the danger of leakage, that is, the danger of permitting the alloy to escape when in fluid or semi-fluid condition.

The heating element which controls the temperature of the alloy may be constructedin various ways, one ofwhich is shown in Figs. 1, 2, 4 and 5. According to this form the terminal screws 24, 28, previously mentioned, screw into brackets 86, 87 which in the physical structure form 'the terminals of the conductors 23 and 27 and of the conductors 25 and 29 of the diagram, Figure 1. These brackets are secured to an insulating panel 88 of any suitable form upon which the apparatus is mounted. These terminals 86, 87 are electrically connected to a heating element 90 as shown in Figure 5 and elsewhere. This consists of a high resistance alloy such as nichrome. In the form shown it is too thin to support the receptacle 82 and hence it is backed up by terminal bars or strips 92 and 96 connected to the respective brackets 86, 87 The parts are provided with suitable insulating spacers 93, 94, 98.

The alloy receptacle 82 is held adjacent to the heating element by means of a clamp or clip 100 consisting preferably of sheet metal having fingers 101 for engaging wings 85 formed on the receptacle. Said clip also has a finger 103 which extends over the top of the ratchet wheel 80 to prevent it and the shaft 81 from rising from their seat on the alloy receptacle.

Under normal operating conditions the fusible alloy 83 is cool enough to be rigid and prevent shaft 81 and ratchet wheel 80 from rotating. Consequently the ratchet wheel is able to hold and prevent the travel of a traveling pawl 102 pivoted upon a pin 104 mounted'in a frame 106 which is slidable upon a guide rod 108 supported in two of the brackets 72. A helical compression spring '110 at one end engages one of the bracket arms 7 2 and at the other end engages the sliding it towards the'left.

ifitatie and arranged that so long the pawl held said switch 40.

Bar 70 may be reset when the alloy 83 is cold b means of a push button 120 shown near the right end of- Figure 1. This controls a spring 122 mounted upon a wall'124 in the apparatus and located in position to tripping. bar and move engage the end of'the in Figure 1. The main switch'arms 13, 14,

15 will remain in closed position under the influence of the electromagnet whose winding 32 is energized as follows: from supply conductor A through the conductor 36 connectedto one 'end of the winding. The circuit is completed through conductor C through conductor 38, controlling switch 40, contact 42,

ping bar 70 will be moved toward conductor 44, stop switch 46, contact 48, conductors 50 and 66, holding switch arm 62 and conductors 60. 4

If now an overload occurs, the heating element 90 will rise to a temperature such as to soften the fusible alloy 83 to a degree sufiicient to permit the ratchet wheel to rotate and release the pawl 102 which is actuated by spring 110. When this occurs, the tri the rig t and open the controlling switch as reviously described' This will break the circuit through the winding 32 which will spring 20 to move bar 18 and-the switc arms rmit 13, 14, 15to open position.

To restart the motor after normal condif tions have been restored and after the alloy has become recongealed, the o erator moves tripping bar 70 towards the le Figure 1 by means of'push button 120. This causes the pawl 102 to reengage its ratchet wheel.

Instead of the type of heatin unit shown in Figures 1 to 5 a modified orm may be used, shown in Figures 6 to -9 inclusive. In

' this form the heating resistance is in the form of insulating material and title ribbon 130 wound around a plate 132 plate 1340f insulating material. These parts are supported upon conductor bars 136, 138 shown in face view in Figured These are electrically energized an the. ends of the ribbon 130 are connected to them respectively for placing the ribbon in circuit. The receptacle, 82 for the fusible alloy is secured by means of a clip 100 in the same manner as before. r

backed up by a the heating element'160 is made heavy and strong enough to serve-the purpose of supporting the receptacle 82% well as heating it. In this type the heating element is secured to the elements 86, scribed. 11 this formv the receptacle 82 is held in position upon the heating element by a clip 100, previously described, the heating element being insulated by means of the insulating plate 152, 15 4. 1

It will be observed that in this apparatus the alloy is heated by conduction, as; the alloy receptacle is clamped to the side of the heating element." This simplifies the labor of assembly and disassembly for repairs and makes it practical to remove the ,heating element when the fusible alloy is cold. Also the receptacle is capable of accommodating an ample quantity of alloy and in addition furnishes the bearings and support for the ratchet wheel and shaft, and prevents escape of the fusible alloy.

It will also be noted holding units are universally or all individually operable upon the tripping bar 70, and yet the bar can be operated by any one of them without disturbing the others. This is due to the lost motion connection between the tripping bar and the fingers 112 of thesliding frames 106, the notches 114 being longer than the travel necessary to open the controlling switch 40. This makes it possible for the. bar

ore being arrests by the finger 112 iii another holding unit.

It is desirable that the notch 71 a long enough to permit bar to be'well under way perspective in Figure 12.

to travel far enough to openthe switch bei 87 previously dethat the heating and l whennioving toward open position as this i will cause the controlling switch to open with a quick break.

Having thus described my invention what I claim as new and desire to secure by ters Patent is:

1. A-device of the class described having a movable circuit controlling element, a rotatable detent for holding it, a vertical solder cup, fusible alloy therein, and means for heating the alloy, the detent having a stem extending down into the cup and having a step bearing in said cup and a lateral bearing.

in the sides of the cup.

2. In a thermal overload relay, a ratchet wheel and shaft, a solder cup containing low melting alloy, a flat heating element, backup strips for reinforcing said heating element, and means for holding the solder cup adjacent to said heating element. O

3. In a thermal relay adapted for polyphase circuits,astrip of resistance material for carrying current, a solder cup clamped to said resistance material, and suitably insulated therefrom, a ratchet wheel having a stem projecting into the cup and cooperating terminals to which the strip is attached, and a movable element for controlling the circuit to be protected, said movable element being engagedby said detent.

4. An electrothermal holding unit adapted to controLa polyphase circuit from one of the phases and having a receptacle, an alloy of low melting point therein, a movable element designed to be held at times and released at times, a rotatable detent for holding and releasing said movable element, said detent having a shaft and said receptacle having a chamber which is cylindrical at the upper end to form a lateral bearing for the shaft, the shaft being of reduced diameter at the lower portion to aflord room in the chamber for thealloy, the lower end of said reduced portion being mounted in the bottom of the receptacle.

5. An electrothermal holding unit adapted for controlling a plurality of circuits from any one of them and having a holding and releasing element, said unit having a receptacle, a fusible substance therein, a detent for holding said movable element, said detent being rotatable at times for releasing saidmovable element when the fusible substance melts, and a heatlng element associated with said receptacle for heating it and the fusible substance, said detent having a vertical shaft,

and the receptacle having a closed bottom for preventing leakage, the bottom forming a step-bearing for the lower end of the shaft.

6. An electrothermal holding unit having a receptacle, an alloy of low melting point therein, a movable element designed to be held at times and released at times for performing the function of the unit, a detent having a shaft revolvable therewith provided with different diameters at different points along 1t, and the receptacle having different diameters at different points to form bearings for said shaft, said bearings being located at a distance from each other and the receptacle being chambered between said bearings for conta ning an ample amount of the alloy. 7. An electrothermal holding unit having a receptacle, an alloy of low melting point therein, a movable element designed to be held at times and released at times for performing the function of the unit, a detent having a shaft revolvable therewith provided with. different diameters at different points along it, and the receptacle having different diameters at difierent oints to form bearmgs for sa1d shaft, 881d bearings being 10- formin the function of the unit, and means for hol g the receptacle close to and laterally separable from the heating element to receive the heat therefrom- 9. An electrothermal holding unit having a heating element, a receptacle, a readily fusible alloy therein, a detent having one portion projecting into said receptacle for being held at times and released at times for performing the function of the unit, and a bendable clip for holding the receptacle close to the heating element to enable it to be heated thereby, said bendable element having a finger overlying the .detent for holding it seated on said receptacle.

10. An overload relay having a control switch, atripping bar for opening it, and a plurality of thermo-electric tripping units, all of which are individually operable upon said bar to move it in a direction to open the switch, each of said tripping units having a movable frame having a lost mot-ion connection with the bar and being biased in a direction to cause the bar to open the switch, a detent for each frame for holding it notwithstanding its bias; a heating element subject to the electrical conditions in the main circuit to be controlled, and a fusible alloy subj ect to the temperature conditions of the heatlng element, said detent being in contact with said alloy to be held or released thereby in accordance with the temperature thereof.

11. An overload relay having a control 1 switch, a tripping bar for opening it, and a plurality of thermo-electric tripping units for moving said bar in a direction to open the switch, said units being-spring-actuated and there being a lost motion connection between the bar and the switch whereby the switch will not be opened until the bar is under way, thereby imparting quick action to the switch in opening.

12. An electrothermal holding unit having a movable element, means for ur 'ng it to move to perform the function of t e device,

a detent for holding it against its biasya fusible alloy for holding and releasing the detent in accordance with its temperature, a receptacle for containing the alloy, a thermoelectric heating element anda bendable sheet metal clamp for holding the heating element adjacent to the outside of the receptacle for heatin it and its contents.

- switch, a thermo-electric heating element, a

for different 7 ing biased in a detent, and a receptacle, a fusible alloy associated with the heating element to be heated thereby, a detent controlled by the alloy in said receptacle, a movable element adapted to be held by said tripping bar for operating said switch, said movable element being biased in a direction to cause the tripping bar toopen the switch, there being a lost motion connection between the movable element and the tripping bar whereby the bar may be moved sufiiciently to open the switch without disturbing the setting of said movable element.

15. An overload relay having a control switch, two thermo=electric heating elements of the main distributing circuit to be controlled, a receptacle, a fusible alloy associated with each heating element to be heated thereby, two detents controlled by the alloyin said receptacles, two movable e ements, each adapted to be held by its respective detent, and a tripping bar for operating said switch, each movable element bedirection to cause the tripping bar to open the switch, there being lost motion connections between the movable element and the tripping bar whereby the bar may be moved by either movable element sufliciently to open the switch without disturbing the setting of the other of said movable elements. I i

16. An overload relay having a control switch, a thermoelectric heating element, a receptacle, a fusible alloy associated with the heating element to be heated thereby, a detent controlled by the alloy in said receptacle, a slidable element adapted to be held in, non-acting position by said detent, a spring for biasing said slidable element in a direction to cause the tripping bar to open the switch, the trip ing bar being longitudinally slidable --receptacle, I

by said ratchet Wheel, a tripping bar operating said switch, said movable element ing element to be heated thereby, a rotatable ratchet wheel controlled by the alloy in said a'movable element adapted to be being biased in a direction to cause the tripping bar to open the switch when the alloy uses sufliciently to permit the ratchet wheel to rotate to release the movable element, there being a lost motion connection between the movable element and the tripping bar whereby when the tripping bar and the movable element have been set'in potentially active positions, the tripping bar may, without disturbing the movable element, be moved to a position in which it will hold the switch open. 18. In a thermal overload relay, a ratchet wheel and shaft, a cup, a low melting alloy therein, a flat heating element, transversely extending means for reinforcing said heating element, and means for supporting the cup adjacent said heating element.

19. In a thermal overload relay, a ratchet wheel and shaft, a cup, a low melting alloy therein, a heating. element, and clamping means for holding the cup adjacent said heating'element, whereby said cup may be readily detached.

20. In a thermal overload relay, a movable circuit controlling element and means releasable upon the establishment of overload conditions in the circuit for normally preventing the movement of said element, said means including a cup, a fusible alloy therein, a stem projecting down into the cup and operatively.

connected to normally prevent the movement of said movable member, said cup being arranged to receive and support the stem, a heating element mounted adjacent said cup, clamping means for detachably securing the cup adjacent the heating element whereby the same may be quickly and easily demounted from attached position and means oo-operating with the circuit to be controlled for ac tuating said heating element, whereby when overload conditions are set up in the circuit, the heating element operates to fuse the alloy in the alloy cup and release the stem.

In witness whereof, I have hereunto subscribed my name.

HERMON L. VAN VALKENBURGI and aving a lost motion connection with the slidable element whereby the bar may he slid to acting position to open the switch without an accompanying motion of the slidable element, and separate means for resettin the tripping bar to non-acting position wit out disturbm the slidable element when the latter is hel by the detent in non-acting position.

17. An overload relay having a, control switch, an electric heating element, a receptacle, a fusible alloyin proximity to the heat- 

